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ZTR repair (won't track straight)

Discussion in 'Mechanic and Repair' started by karlInSanDiego, May 8, 2003.

  1. karlInSanDiego

    karlInSanDiego LawnSite Member
    Posts: 10

    Actually it may turn into more of a light restoration. Forgive me for crashing your pro boards, as I'm a homeowner with an acre and a half of mostly slope. I'm getting ready to buy a 10 year old front deck Grasshopper 1600BT ZTR (44" deck) that's a commercial mower's old workhorse. It's been sitting for about 6 months, and besides now needing a battery and correcting a side chain that keeps popping off (suggested chain is too worn or cog needs alignment)

    here's the kicker- one side's not turning the same as the other (in other words, it only cuts donuts)
    now he claims that this happened before to the same mower and he only had to replace a worn spider gear (sits between the motor's driveshaft and the hydro unit) He claims it's not too bad of a job to pull the whole hydro out (but apparently, this mower's past its prime for him and not worthy of the time), and that the $5.00 spider gear is the reason why that wheel stopped driving. I did see it as an available replacement part along with the couplings to each side of it, but would this worn part be enough to trash the turning of the mower? It's still in place and didn't appear obviously worn by simple visual inspection.

    I'll probably buy it no matter what, as he's only asking $300, but I'm wondering if these aren't the same symptoms you'd experience when a hydro needs rebuilding/replacing. On that note, they're roughly $700 for each hydro unit new (assuming I can find one). Have any of you had any luck rebuilding a hydrostatic motor, or have you had one rebuilt by local shop for a reasonable rate?

    One final thought. When rebuilding brakes, suspension on a car, the rule of thumb is to do both sides at the same time. Though the job will take twice the time, would you recommend replacing the spider gear on both sides at the same time to try to prevent otherwise inevitable downtime? How would you approach this same philosophy when it comes to rebuilding the hydro unit(s)?

    Thanks for any advice you can give. I've already started to learn a some good tips about cutting by reading your boards.
    coupler spider
  2. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    could be the swash plate is cracked or broken on that Eaton hydro. any hydro work is an advanced homeowner project. if you call the grasshopper tech line he will walk you through it.
  3. karlInSanDiego

    karlInSanDiego LawnSite Member
    Posts: 10

    Thanks for the info. Do you know any way of testing for a fault on the Eaton Hydro, short of breaking it apart and inspecting the insides? These units, although they have a fluid in and out from resevoir, are self contained. I don't believe by the looks of the fittings (along with the lack of a separate pump) that the system is pressurized outside of the unit. Are replacement swashplates available? If not the swashplate, I imagine you could have problems with individual pistons not sealing, right?
  4. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    I'm sure there is some kind of test but it's easier for me to just crack them open. It has ball pistons. Get a manual.
  5. karlInSanDiego

    karlInSanDiego LawnSite Member
    Posts: 10

    Turns out my mower is a 1979 model. I guess I'll need to tear one of the hydrostats out to find out who made it and what the model is.

    I got the mower's operator's manual/parts list from Grasshopper, but its diagram shows hydro transmissions with swash plate pivot bolt on the bottom (like modern eaton designs.) My units have an external shared resevoir, a line in on the top and line out on the bottom, and the swash pivot (attaches to steering linkage) is on the top of the Xmission.

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